The following U.S. Patents are incorporated herein by reference:
U.S. Pat. No. 8,968,167 discloses a resistance system for an exercise device including a plurality of cord plates which may be selectively engaged by one or more pins which may include an engagement lock. One or more of the cord plates may be received by a pin with each cord plate that is received by a pin being secured relative to a frame. A cord plate that has received a pin is engaged and a cord plate that is not received by a pin is disengaged. A carriage may be provided which receives a plurality of elastic cords which may be attached to the cord plates. The carriage may be displaced relative to a base frame, to provide elongation of the elastic cords coupled to engaged cord plates and no elongation of the cords coupled to the disengaged cord plates which provide a selective resistance for a user.
U.S. Pat. No. 7,981,014 discloses a resistance system for an exercise device including a frame, a resistance element such as elastic bands, coil springs, weight plates, pneumatic or hydraulic cylinders. An interference element such as a plate, chain or one or more links is supported by a support plate mounted on the frame. Selective engagement with the resistance element is provided by actuation of a dial, other actuator or controller or directly by the user. Thereby the resistance element can be selectively engaged or disengaged to vary the resistance to the user.
U.S. Pat. No. 7,887,468 discloses a resistance system for fitness equipment including a frame, a resistance source such as an elastic cord, coil or any other type of spring, weight, pneumatic or hydraulic cylinders. The resistance source is mounted to a resistance block with a load support. A support disk is provided that is movably mounted to the frame and adapted to enable selective engagement with the load support. A transmission member, including a pliable member such as a cable, belt or other member, is coupled to the resistance source. Movement of the support disk enables selective engagement of the resistance source. In this way one or more individual resistance sources can be selectively engaged or disengaged to vary the resistance to the user by actuation of a dial or other actuator as directed by the user.
U.S. Pat. No. 7,597,653 discloses an exercise apparatus having a rotary camming disc selectively configured to engage respective locking pins for engaging and disengaging selective numbers of force resistors for varying exercise resistance.